The are two search areas on Linux App Finder. One is located on the top right hand corner of every page and uses Google to search the site. The other appears only on the category and most viewed pages. It is located just above the list of apps on each page.
Until recently the latter search could only match a single word or phrase. I'm pleased to announce that the capabilities have been extended to use boolean searching.
By default any space is treated as an OR. You can also explicitly call out AND, OR, and NOT as options. If a phrase is what you are looking for then placing quotes around it will keep the words as a single search item.