What software can read this sub file?

[LogicDeLuxe]

It begins with that (and has many more such lines)
{1}{1}29.97
{6639}{6684}You think she's still alive?
{6687}{6763}I mean, that she actually could|have survived?
{6766}{6809}Who?
I'm looking for a way to make a sup file out of it, which can be used in IfoEdit or MuxMan, preferably a simple converter. Does it look familiar to you?

[CoNS]

It's MicroDVD's SUB format, which is the second most common text subtitle format in the world, next to SupRip's SRT format...

The file extension should be .sub.

You can convert it to a SUP file (bitmap subtitles) using SubtitleCreator (see sticky thread in this forum section). The first line in your quoted subtitle file shows the frame rate.