Is there no way to update ARD to 3.8 without updating to OS 10.10?

I think Apple is blocking it through the App store, but there are a few third party sites that offer the app package as a download that you could try. Obviously your license code would still be needed when it launches for the first time.

I found this:

https://kickass.so/apple-remote-desktop-3-8-mac-os-x-coque599-t10140155.html

I downloaded 3.8 from Apple's developer's download site, and it worked great in 10.9.5.

Until today, when I get the message "This copy of Remote Desktop has expired".

So I'm in the same boat: how can I run 3.8 under 10.9.5? I have a legit paid-for license.

It looks like the official compatibility in the App Store is "10.9 or later" so it should actually allow you to download and install it from the store in 10.9. You will almost certainly need to delete the version you have and reinstall fresh from the store or the original install disk and then have the app store update it for you.

Under 10.9.5 :

I deleted the seed version of 3.8 (finder delete the app, empty trash).

Then I re-installed using my official 3.0 DMG.

The app installs OK, but when I run it, I get the message "Remote desktop is installing required software components. A newer version of this software already exists on this disk." If you click "continue" you get "The remote desktop administrator software failed to start due to an unexpected error."

Update: After several tries, I was still not able to get the official App Store version of ARD 3.8 working in 10.9.5 - I used time machine to go back to my previous version (3.7.2) - which notably caused me to lose my stored passwords, but fortunately I have copies of them.

So I'm back at 3.7.2 and waiting to see if anyone else can find a way to get the official 3.8 version running under 10.9.

I took another look through things and found this:

About Remote Desktop Admin 3.8 - Apple Support

It appears that you can only upgrade to 3.8 from an originally purchased disk version by also upgrading to Yosemite first. The functionality to upgrade a non-app store purchased copy doesn't seem to be available for 10.9 computers, but you can still purchase it from the App Store from within 10.9

I have a 10.10 test machine running. I installed ARD from my original DMG. Then the app store saw that it needed an upgrade to 3.8. After signing in it updated it. I then compressed it and copied to my 10.9.4 computer. After unzipping I now have 3.8 running fine on 10.9.4.

If you have VMWare Fusion or Parallels Desktop, you can install 10.10 inside a virtual machine...

If you really want the ARD update create a temp partition on your current drive or any spare drive you have, install 10.10, update ARD then delete the partition. Bit of work but will get you what you want.

Yes, temporary install at 2nd partition will do it.

I had a different kind of problem - already at OS X 10.10.2 and not being able to update to MAS-only ARD 3.8 no matter what I did.

I followed Installing Apple Remote Desktop 3.3 in OS X Lion or later - Apple Support but to no avail. Some people also hinted to switch the system language to English and restart, however I was already using English.

In the end I installed a temporary OS X 10.9.5 in a virtual machine, then installed ARD 3.3 there as described in those instructions referenced above. That let me to update to ARD 3.7.2 which I did (this was actually possible even at OS X 10.10.2 as well but then I couldn't get 3.8 there), then I upgraded to OS X 10.10.2 and finally was able to update to ARD 3.8. That added it into my purchases and now I can install it at my primary system and delete the temporary virtual machine.

No idea what causes the troubles detecting the non-MAS ARD installations, but it's quite insane.