Can forum members contribute to the game's lore?

Self-explanatory. Some forum members have written stories and characterization for various Heroes, so it would be awesome SG give us some credits for making the game more enjoyable.
Of course, there will also be an effort to add continuity and consistency to any added lore, and there will be some quality control on it as well - spelling or otherwise.

That would be a dream come true.

But for the same reason people excuse Harry Potter being some two dimensional, I expect SG would argue that they are being inclusive by leaving it to our imaginations!

Another way to think of it though, is that SG own everything written on the forum, which is in the terms of use.

Therefore, as they own all the fan fiction and allow it to perpetuate, they are giving tacit agreement to it’s authenticity.