Разумеется, не равно, но в условиях лицензирования разницы практически нет. Критерии OSI и FSF почти эквивалентны.
https://www.gnu.org/philosophy/open-source-misses-the-point....
>The two now describe almost the same category of software, but they stand for views based on fundamentally different values.
>In practice, open source stands for criteria a little looser than those of free software. As far as we know, all existing released free software source code would qualify as open source. Nearly all open source software is free software, but there are exceptions.
>The official definition of “open source software” (which is published by the Open Source Initiative and is too long to include here) was derived indirectly from our criteria for free software. It is not the same; it is a little looser in some respects. Nonetheless, their definition agrees with our definition in most cases.https://www.gnu.org/philosophy/free-open-overlap.html
>Among all programs that are open source, only a minuscule fraction are not free. If the bottom row were drawn to scale, its text would have to be in a tiny font, perhaps too small to read.
(нужно ещё добавить, что эта информация «all existing released free software source code would qualify as open source» не вполне верна и FSF одобрил несколько «закрытых» лицензий. Но это всё единичные случаи)
В частности, повторяю, лицензия GNU glibc (LGPL v2.1) является открытой:
https://opensource.org/licenses/lgpl-2.1.php
Лицензия musl (одна из «лицензий МТИ», которую FSF называет «Expat license») является свободной:
https://www.gnu.org/licenses/license-list.en.html#Expat
Поэтому противопоставлять в отношении открытости или свободности две открытые и свободные реализации стандартной библиотеки C категорически неверно.
