Hello!
I just wanted to make sure. Am I allowed to check these into source control on an open source game I'm building? The game is hosted on Github.

To begin with I'm just thinking about the free part of Tiny Swords. But I'm also interested in if I'm allowed to check in the paid part as well in case I purchase that in the future.

Also, these looks great! Keep up the good work :)

• Feel free to use this asset pack in both personal and commercial projects, modifying the assets as needed.  
  
• Crediting is not required, but it helps and is always welcome. 
• You may not redistribute, resell, or repackage the assets, even if the files are modified. 

No! I don't think you can commit the assets into a public Github project, private should be fine as long as you don't give it to everyone. What people usually do is provide a link to the asset page and ask people to download them and place them into an appropriate folder in the project, you can have some placeholder assets that will make the game work in the meantime.

Also It seems that there is another asset pack with CC0 licensing, CC0 allows you to do whatever you want with it but it's completely different that the current one.