Regarding the issur of Lo Techanem, does this apply to giving answers to online Q&A sites such as Stack Overflow, where most likely the questioner is not Jewish?
Tosfos understand that "Darchei Shalom" is not considered a gift. IMHO that means since you benefit from the resulting peace then it's not a free gift since its win-win for both sides. Similarly when you contribute to an online community you benefit that when you need assistance the online community will be available to help you. So it seems that since it's win-win it's not considered a "free gift".
The Rambam seems to understand that the issur was enacted so a person won't learn from gentiles' ways and get close to them. So again IMHO since online public community forums which are focused on work related topics seem not to foster a personal relationships with those you interact with it would be ok.