Update readme.md

readme.md

@@ -88,7 +88,9 @@ POST https://emkc.org/api/v2/piston/execute
 
 > Important Note: The Piston API is rate limited to 5 requests per second. If you have a need for more requests than that
 > and it's for a good cause, please reach out to me (EngineerMan#0001) on [Discord](https://discord.gg/engineerman)
-> so we can discuss potentially getting you an unlimited key.
+> so we can discuss potentially getting you an unlimited key. What is and isn't a good cause is up to me, but, in general
+> if your project is a) open source, b) helping people at no cost to them, and c) not likely to use tons of resources
+> thereby impairing another's ability to enjoy Piston, you'll likely be granted a key.
 
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