If people have your iCam login and password, the only thing they will be able to do is view your webcam through an iCam client, such as the iCam app or iCamWeb. They can't use that login and password to get any other access to your computer (assuming that your iCam login/password is different from the login/password you use to login to your computer).
You can give iCamWeb access to your cameras without giving out your login and password. When you login to iCamWeb, there is a Share link at the bottom of the page. You can give that Share link out, and people can use that link to view your webcams. That Share link is uniquely tied to the login/password, so if you want the Share link to stop working, you just need to change the login/password in iCamSource.
