If this is the first time you have looked at mumsnet, then you probably need to spend more time reading before you decide what this massive massive forum is all about and make any sort of judgement.
Yes, there is swearing. This is fine. We are all adults and there are many forums on the net where swearing is not permitted, for those who do not like to read the words to go and feel comfortable.
On this site, it has been decided by the owners that we can cope with some naughty words.
I'm not a big fan of the swearing. Personally I don't think it's necessary except perhaps in the most extreme cases, I find gratuitous swearing dull, frankly. However, I like this place and I accept that swearing is not banned and if I am not happy, I have the choice to skip the post, close the thread or log off.
This subject has been raised quite often and discussed at length, and it always ends that some people hate it, some people love it, most people aren't that bothered one way or the other and things are going to stay just as they are.