@hyc Speaking (only for myself) as someone who refused to use the "open source" term for a very long time, "giving back" isn't part of the bargain from my point of view.
To me, Free Software means that you can privately use the software however you'd like with no obligations "back" to the original author. Non-private use has limited obligations.
If you want to *protect* and *propagate* those freedoms for *others* (farther downstream), use a copyleft license.