> By accepting this agreement and using the software you agree that Microsoft may collect, use, and disclose the information as described in the Microsoft Privacy Statement [...]
Doesn't make it okay, just legal
https://www.microsoft.com/content/dam/microsoft/usetm/docume...
E.g. when JavaScript was designed, they didn't need to know that typescript would be invented to know how JavaScript would look.
Dog-fooding a language by writing a compiler in it can lead to the designers adding language features to make compiler development easier, even if they detract from the design of the language for the 99% of users who aren't writing a compiler.
SPy is a compiler. SPy is not a compiler for OCaml. SPy is not a compiler for COBOL. SPy is not a compiler for Python.