"I'm participating in lectures about linguistics" and "I participate in lectures about linguistics", without an adverb, both interchangeably mean the same thing in English
Technically maybe, but in real use, just about every native English speaker will understand the first to mean that I'm doing it right now and the second to mean that I do it habitually.
There is no viable alternative to Flash right now for streaming live video, especially with the same market penetration.
Yes there is, it's called RTSP/RTP and it's well-supported by VLC and QuickTime (and by extension their browser plug-ins). http://en.wikipedia.org/wiki/Rtsp