Yes Alio I definitely think you should put the programme on the website.

Most other festivals with any cred do, and (I hear reliably) this does little if anything to the detriment of programme sales.
I always buy a programme, whether I already have the content of the all-important "middle pages" in advance or not. Yes Keith is absolutely right, most folkies will buy a programme to support the festival and as a souvenir, also to get all that extra information such as maps, local adverts and biog details that don't appear on the website in most cases.
The big bonus point though is that folks can make plans based on more accurate programme information from the website, they can be sure of coming on the right day/evening to see specific artistes or participate in a specific workshop or singaround (how infuriating are the sites that just say "plus workshops, singarounds, sessions" then when you arrive you've just missed one...).
If I'm travelling a longer distance, I really do need to know whether planning to arrive in a strange town at - say - midday on the Saturday will mean I miss a vital event or whether the local streets would be closed for a parade etc etc. And on a Friday, whether events start up from midday or from 7 pm...

But probably most important, the festivals concerned end up getting more revenue from those folks who are pre-informed, who will then come and enjoy with confidence and then next year perhaps decide to buy a whole weekend ticket because they were so impressed with the festival and its user-friendly publicity and attitude this year...

So - go for it, Alio!