You can have as many derived projects as you want but a derived project cannot be copied. Project 139129 was derived from another project (so it has no save a permanent project button) while project 39040 is not (it is a top level project so you can save a permanent copy of it).
The UI's treatment of this is not very intuitive and we some work queued to address that. There some additional discussion about the reason for this disconnect over on this thread,
Sean