I am a dev myself and I am affected. The error is "Unathorized". Here is the debug log from CommerceKit (defaults write com.apple.appstore ShowDebugMenu -bool YES) + turn on the debugging in the menu.
http://postimg.org/image/svh3a253r/
Sep 30 21:23:16 Mareks-MacBook-Pro.local storedownloadd[353]: CheckPreflightOperation: Downloading remote pre-flight from http://a948.phobos.apple.com/us/r1000/045/Purple/v4/aa/6e/19/aa6e190c-00cb-30b8- 1979-2dd175e04f90/signed.dcr.8346782470779595945.pfpkg
Sep 30 21:23:16 Mareks-MacBook-Pro.local storeaccountd[287]: ADI: Account is not provisioned, omitting OTP and MD
Sep 30 21:23:16 Mareks-MacBook-Pro.local com.apple.CommerceKit.TransactionService[1504]:
--------------------------------------------------------- Begin --
System Version 10.10.5 (Build 14F27)
"com.apple.CommerceKit.TransactionService" Version 1.0 (1)
-------------------------------------------------------------------
Sep 30 21:23:16 Mareks-MacBook-Pro.local com.apple.CommerceKit.TransactionService[1504]: xpc_add_bundle /System/Library/PrivateFrameworks/CommerceKit.framework/XPCServices/com.apple.C ommerceKit.StoreAEService.xpc
Sep 30 21:23:16 Mareks-MacBook-Pro.local storedownloadd[353]: -[ISURLOperation _logRequest:]: Sending request for http://a948.phobos.apple.com/us/r1000/045/Purple/v4/aa/6e/19/aa6e190c-00cb-30b8- 1979-2dd175e04f90/signed.dcr.8346782470779595945.pfpkg
Sep 30 21:23:16 Mareks-MacBook-Pro.local storedownloadd[353]: Logged "Request"
Sep 30 21:23:17 Mareks-MacBook-Pro.local storedownloadd[353]: CheckPreflightOperation: remote pre-flight downloaded to file:///var/folders/j9/6r68cvfs2814zd84v4d0lsx80000gn/C/com.apple.appstore/4913 90884/preflight.pfpkg
Sep 30 21:23:17 Mareks-MacBook-Pro.local storedownloadd[353]: ---------- Logged NSData in "/Users/xhruso00/Library/Logs/storedownloadd/2015-09-30 21:23:17.584 (ResponseBody_signed.dcr.8346782470779595945.pfpkg).dat"
Sep 30 21:23:17 Mareks-MacBook-Pro.local storedownloadd[353]: CheckPreflightOperation: Running local pre-flight from file:///var/folders/j9/6r68cvfs2814zd84v4d0lsx80000gn/C/com.apple.appstore/4913 90884/preflight.pfpkg
Sep 30 21:23:18 Mareks-MacBook-Pro.local storedownloadd[353]: PKDistributionController: Performing disk space check with 3178680320 bytes available on disk, 0 bytes alreay downloaded and 329752576 required bytes (installSize=8864768 + fileSize=6315008 + paddedSize=314572800)
Sep 30 21:23:18 Mareks-MacBook-Pro.local storedownloadd[353]: CheckPreflightOperation: verified preflight success=1, error=(null), distController=<PKDistributionController: 0x7fbebac6cd50>
Sep 30 21:23:18 Mareks-MacBook-Pro.local storeaccountd[287]: ADI: Account is not provisioned, omitting OTP and MD
Sep 30 21:23:18 Mareks-MacBook-Pro.local storedownloadd[353]: -[ISURLOperation _logRequest:]: Sending request for http://a1.mzstatic.com/us/r30/Purple4/v4/88/e6/6f/88e66fd6-6951-9934-57e3-dbd46f 1fe294/icon512-2x.png
Sep 30 21:23:18 Mareks-MacBook-Pro.local storedownloadd[353]: Logged "Request"
Sep 30 21:23:19 Mareks-MacBook-Pro.local storedownloadd[353]: ---------- Logged NSData in "/Users/xhruso00/Library/Logs/storedownloadd/2015-09-30 21:23:19.885 (ResponseBody_icon512-2x.png).dat"
Sep 30 21:23:19 Mareks-MacBook-Pro.local storedownloadd[353]: DownloadQueue: Cached receipt for <SSDownload: 0x7fbebac61880> to /var/folders/j9/6r68cvfs2814zd84v4d0lsx80000gn/C/com.apple.appstore/491390884
Sep 30 21:23:19 Mareks-MacBook-Pro.local com.apple.WebKit.WebContent[1498]: ISPropertyListProvider: Adding download found in xml protocol - iQR codes - QR Code Art Studio
Sep 30 21:23:19 Mareks-MacBook-Pro.local storeassetd[347]: SoftwareMap: No app was found with bundle ID com.hrubasko.iQR to upgrade to 1.9
Sep 30 21:23:19 Mareks-MacBook-Pro.local storedownloadd[353]: sending status (iQR codes - QR Code Art Studio): 0.000000% (0.000000)
Sep 30 21:23:20 Mareks-MacBook-Pro.local storedownloadd[353]: DownloadManifest: removePurgeablePath: /var/folders/j9/6r68cvfs2814zd84v4d0lsx80000gn/C/com.apple.appstore/491390884
Sep 30 21:23:20 Mareks-MacBook-Pro.local storeassetd[347]: SoftwareMap: No app was found with bundle ID com.hrubasko.iQR to upgrade to 1.9
Sep 30 21:23:20 Mareks-MacBook-Pro.local storedownloadd[353]: AuthorizationController: Non-interactive authorization succeeded
Sep 30 21:23:20 Mareks-MacBook-Pro.local storedownloadd[353]: AuthorizationController: authorizing PKInstallClient and SUAppStoreUpdateController
Sep 30 21:23:20 Mareks-MacBook-Pro.local storeassetd[347]: SoftwareMap: No app was found with bundle ID com.hrubasko.iQR to upgrade to 1.9
Sep 30 21:23:20 --- last message repeated 2 times ---
Sep 30 21:23:20 Mareks-MacBook-Pro.local storedownloadd[353]: ISStoreURLOperation: Starting URL operation with url=http://osxapps.itunes.apple.com/apple-assets-us-std-000001/Purple/v4/03/1a/73/03 1a73b8-940f-6d47-8bec-247b621c468a/mzps7779267149677748840.pkg / bagKey=(null)
Sep 30 21:23:20 Mareks-MacBook-Pro.local storedownloadd[353]: -[ISStoreURLOperation _runURLOperation]: _addStandardQueryParametersForURL: http://osxapps.itunes.apple.com/apple-assets-us-std-000001/Purple/v4/03/1a/73/03 1a73b8-940f-6d47-8bec-247b621c468a/mzps7779267149677748840.pkg
Sep 30 21:23:20 Mareks-MacBook-Pro.local storeaccountd[287]: ADI: Account is not provisioned, omitting OTP and MD
Sep 30 21:23:20 Mareks-MacBook-Pro.local storedownloadd[353]: <HashedDownloadProvider: 0x7fbebac6af00>: Opening file /var/folders/j9/6r68cvfs2814zd84v4d0lsx80000gn/C/com.apple.appstore/491390884/m zps7779267149677748840.pkg returning file descriptor 12 (0 streamed)
Sep 30 21:23:20 Mareks-MacBook-Pro.local storedownloadd[353]: -[ISURLOperation _logRequest:]: Sending request for http://osxapps.itunes.apple.com/apple-assets-us-std-000001/Purple/v4/03/1a/73/03 1a73b8-940f-6d47-8bec-247b621c468a/mzps7779267149677748840.pkg
Sep 30 21:23:20 Mareks-MacBook-Pro.local storedownloadd[353]: Logged "Request"
Sep 30 21:23:20 Mareks-MacBook-Pro.local storedownloadd[353]: Logged "Response_mzps7779267149677748840.pkg"
Sep 30 21:23:20 Mareks-MacBook-Pro.local storedownloadd[353]: sending status (iQR codes - QR Code Art Studio): 0.000000% (0.000000)
Sep 30 21:23:20 Mareks-MacBook-Pro.local storedownloadd[353]: AssetDownloadOperation: Subtracted 0 already-downloaded bytes from required space (now requires 207 bytes)
Sep 30 21:23:20 Mareks-MacBook-Pro.local storedownloadd[353]: ISStoreURLOperation: Chose not to retry after error: Error Domain=ISErrorDomain Code=1 "The server gave an error during download: 401 Unauthorized." UserInfo=0x7fbebadaccb0 {ISHTTPURLResponseStatusKey=401, NSLocalizedDescription=The server gave an error during download: 401 Unauthorized., NSLocalizedFailureReason=Unauthorized}
Sep 30 21:23:20 Mareks-MacBook-Pro.local storedownloadd[353]: AssetDownloadOperation: Asset download cancelled/failed. Will do retry #1? 0
Sep 30 21:23:20 Mareks-MacBook-Pro.local storedownloadd[353]: DownloadOperation: Download failed with error: Error Domain=ISErrorDomain Code=1 "The server gave an error during download: 401 Unauthorized." UserInfo=0x7fbebadaccb0 {ISHTTPURLResponseStatusKey=401, NSLocalizedDescription=The server gave an error during download: 401 Unauthorized., NSLocalizedFailureReason=Unauthorized}
Sep 30 21:23:20 Mareks-MacBook-Pro.local storeassetd[347]: SoftwareMap: No app was found with bundle ID com.hrubasko.iQR to upgrade to 1.9
Sep 30 21:23:34 Mareks-MacBook-Pro.local storedownloadd[353]: sending status (iQR codes - QR Code Art Studio): 0.000000% (0.000000)