No. You must pay for v10.7 Lion. You can purchase Lion from the App Store (if you have Snow Leopard v10.6.6 minimum installed) or you can purchase the thumb drive from the Apple online store.
Make sure your Mac meets Lion's requirements ..
- Mac computer with an Intel Core 2 Duo, Core i3, Core i5, Core i7, or Xeon processor
- 2GB of memory
- OS X v10.6.6 or later (v10.6.8 recommended)
- 7GB of available space
In addition to what Carolyn said, you have meet the hardware requirements for Lion: at least an Intel Core 2 Duo, i3, i5, i7, or Xeon processor, 2 GB ram though 4 GB works much better, and 7 GB free space on the hard drive.
If you want to do development work, you will need at least 4 GB ram to work efficiently.
You also will need to look into Xcode for Lion, available to registered developers.