Check on your website (ftp) for something called cgi-bin (at root).
if you see various php-cgi (php5-cgi, php4.cgi) files, you might also have a php.ini file.
If you have that, download the php.ini file and open it in a text editor like Word pad (not Microsoft word)
Search for safe mode in the file, and change true to no, on to off, whatever it is. I haven't looked.
Upload the php.ini file and overwrite the existing copy.
If you do not have a php.ini file in your cgi-bin I recommend asking your hosting company to allow you individualised control over php by having one.
There are other really important php settings here that may be useful to you down the road, for example, upload file sizes, memory sizes, etc. that will prevent server side errors when your users start to interact with the forms in a ojs installation.