Hi Tim, 

I've had a look at the code in the past but haven't actually used the service myself.

The code doesn't follow Moodle coding guidelines very well - lots of stuff that I would usually consider bad practice -  Davo Smith from Synergy Learning spent a chunk of time cleaning some of it up and making sure it was safe, but since then various other developers have worked on the code and I don't know if any Moodle Partners have reviewed the latest code to check how safe it is to use. Hopefully Davo might chime in here?

One major thing to be aware of: It only supports the "assign" and old 2.2 assignment module in Moodle (Turnitin supported workshop/forum activities as well)

There are a few other plagiarism plugins that might be worth considering as a replacement for Turnitin in the Moodle.org Plugins directory here:
https://moodle.org/plugins/browse.php?list=category&id=35

A good thing to look at is how many registered sites are using those plugins - look for this image:

Well... I used to hate Turn it In with a fiery passion -- not because of their product (it's a great product), but because schools can't create an own the student accounts. So it was always a nightmare the first week of school when getting students and teachers to sign up for an account (and to do it correctly). HOWEVER, with the Moodle plugin, I absolutely love Turn it In now!

We are on Moodle 3.0 and this is our first year using the TurnitIn plagiarism plugin (which requires you to also download the Turn it in Direct V2 Assignment module for configuration purposes, but you don't need to actually use this depending on how you use Turn it In)-- We use the plagiarism plugin tool simply to get the originality scores to appear in Moodle instead of having kids go out to Turn It in to upload their work, which then require teachers to log into turn it in to check these scores.

So, now it's all done though Moodle and it's been an amazing experience! No more issues with kids forgetting their turn it in account info. They just submit their work in Moodle like they normally do, and a turn it in score optionally appears beneath their submission if a teacher enables it (there is a screenshot in the first link above).

This plugin integration costs a dollar per student on top of the normal turn it in cost, but this has been completely worth it for my tech department -- teachers and students no longer have to worry about correctly creating and managing their own Turn It In accounts. They also like that they don't have to log into the Turn it In website at all and more which has been a time saver, and a Tech Support dream : )

I am interested in plagiarism checkers, but not commercial ones.  Any recommendations?

Global checking is fine, but more important is internal checking of past assignments within our own student body. 

Hello everyone,

You have a great discussion going on – it was very interesting to gather some insights about your opinions on Turnitin and PlagScan. As PlagScan's communications manager, please allow me to comment on the aspects mentioned above about PlagScan's compatibility with Moodle, switching from Turnitin and pricing:

We are aware of some imperfections of our code that have impaired PlagScan’s compatibility with Moodle. We have spent much time focusing on improving other aspects of our software in the past. However, we have noticed a vast increase in traction with our Moodle integration recently and are now rebuilding the code to enable a flawless integration to Moodle as one of our top priorities. If anyone is interested in receiving closer details or receiving access to a beta-test, please feel free to get in touch with us at info@plagscan.com. We also value feedback and are always open to new ideas and suggestions. 

PlagScan is very flexible and open to helping customers. We have assisted multiple users to switch form their previous plagiarism software to our service by offering a script to move existing archived documents into the comparison pool. We have received a lot of positive feedback from customers who switched to PlagScan. A majority of customers who switched, have remained with our service. 

We actually offer a special discount for users who intend to switch to PlagScan from are a different plagiarism software, such as Turnitin.

Our pricing is fair and customized to our user’s needs. Particularly the pricing packages for organizations are well-calculated. Users can always reach out to us if they have any concerns, especially if they feel inadequately charged. 

I hope this helped. Feel free to reach out if you have any questions!