That source engine license could be a bit pricey...
Q. Can I sell my Source Engine game on Steam?
A. Yes, but there are a few requirements:
You will need to complete an additional agreement for distributing a paid Source Engine product on Steam.
If you are using the RAD tools included with the Source SDK, you will need to contact RAD for information and cost associated with licensing MILES and/or BINK.
For any Source Engine game that charges money, Havok needs to be paid a licensing fee of $25,000 for the physics engine. You will need to pay this fee up front before making your game available for sale on Steam.
You can only sell your Source Engine game via Steam unless you get a full Source Engine license.https://partner.steamgames.com/document ... urce_games