Edit : I saw some comments on the jyjfiles which were contesting/doubting some facts stated in the petition and asking for evidences. I'm gonna post a few links which I think prove that what is written in this petition is based on articles and solid facts. Feel free to check the sources.
Plus this link, wich proves that in the past SM and some other big companies already bribed broadcast stations etc. and used not so legal methods to do business and earn money (this is an old article but unfortunately not much has changed in the korean music industry after all these years) :
And then for those who still claim that JYJ's contracts are fair and legal here is an interesting and very similar case which is Kevin Woo's (from UKiss) case :
I know it's a lot of articles to read and I'm sorry I just copied/pasted the links without really organizing them chronogically but otherwise it would have taken me too much time ^^" Though, if you're really interested in JYJ/TVXQ and wish to know more about the lawsuit, all the controversies it provocated etc. I warmly encourage you to read all the articles linked above and then to form your own opinion on the matter.