I have seen titles, such as books or business names, that omit the apostrophe. Is this proper? Can a title be apostrophe free if the author chooses? EX: Tom and Sallies Big Adventure. Should Sallies properly be Sallie's? Or Sallies'?
Apostrophes should be used in titles as in body text. To omit an apostrophe can change the meaning of the words.
There may have been some historical scenarios in which they’ve been omitted for technical reasons (e.g. apostrophes in filenames used to cause issues, though I can’t think of any good reason why they’d be omitted in printed headings or titles.