Yes, you can buy multiple domain names and redirect it to one domain name. In that case, you would only need to purchase one software license for the one domain name you are redirecting to, and install the software onto that domain/web server. We provide web hosting packages / domain names under the top menu "Purchase & Download" tab.
There are some cases where we would recommend buying multiple domain names and redirecting them to one domain name, but also cases where we would not.
Namely we wouldn't recommend buying various domain names with certain keywords and redirecting those to your main domain name in an effort to get higher traffic/SEO. We would recommend following the SEO tips to increase your traffic rather than that which we wouldn't say is effective.
Related: How To Get Your Website On The First Page of Google
It is known that Google does not rank websites that are posting duplicate content favorably. Redirecting domains to one domain doesn't have that issue necessarily as it is just a redirect, though again, we don't find it to be an effective way to increase traffic or popularity. Perhaps it would be useful for advertising materials.
The situtations where you may want to purchase multiple domain names and redirect them to your main domain name? Situations similar to how craigslist.org has the craigslist.com redirect to not lose traffic to users entering that .com url instead of .org, or if you want to provide different services - like for a commercial side/nework side you may want to do .com and .org for example. We cover this topic more in our blog posts:
"Should you get the .com, .org, .net, .biz., country tld … all tld’s … or what?"
"Should you get .com, .org, and .net domain names – all the tld’s?"