The Open Source Definition [0] cares about more than just "that source code shall be available". Among other things, it says "The license must allow modifications and derived works" and "The license must not restrict anyone from making use of the program in a specific field of endeavor".

In fact, the OSD is nearly identical to the Debian Free Software Guidelines [1].

[0] https://opensource.org/osd

[1] https://www.debian.org/social_contract#guidelines