For BetaCopter go to https://github.com/olliw42/ardupilot/branches, and pick a BetaCopter branch.

For licenses, terms of usage, acknolwedgments, and so on, go to the same link and pick a BetaCopter branch.

For your convenience, binaries are also hosted here for download:

• ArduCopter-v2.px4
• ArduCopter-v3.px4
• ArduCopter-v4.px4

Please see http://www.olliw.eu/storm32bgc-wiki/STorM32-ArduPilot for information on the usage and features of BetaCopter.