An important aspect of ITIL is the "open-source" nature of its practices. Explain?

ITIL itself is a collection of industry best practices in the area of IT service management.  It is vendor, product, platform, protocol and system independent . Hence it is conceptually applicable in all situations and for all customers who rely on IT servies in their business modelMaybe this is why we consider ITIL to be open source !!

From another angle, there are software applications, templates, forms ,,,, etc that support ITIL/ITSM ans are freely available as open source ... hence the description "open source"

In my point of view i do agree totaly with Mr,: Mohammed thiab ,s answer

It is vendor, product,platform,protocol & system independent

&

in the same time i converted by Mr,: Abubaker,s answer as well

Open source denotes the ability to adjust the business process on your own to match your needs. I expect that the same meaning is carried out on ITIL practices where they are clearly outlined for all to see and understand the reasons behind those practices being best practices.

Thanks for inviting me to answe this question. But I am sorry I am not from IT background.

Is it because, it promotes collaboration in public for continual improvement?

Thanks for inviting me 

In spite of the question is out of  my  background but I saw it is an important question and I need to followup the answers 

It is fully right!

An important aspect of ITIL is the "open-source" nature of its practices.

That is because ITIL was not created by and is not owned by any private company. 

The ITIL portfolio was originally developed for UK government, and is valuable; the government periodically requests tenders for private-sector partners to manage it. Historically, this had been APMG (http://www.apmg-international.com) up to Mar.2013. However, in April2013 Capita won the contract, under a new arrangement which required them to invest in a joint venture. This joint venture, called Axelos, was formed in July2013, and it took over from APMG on01 January2014.

Axelos is a joint venture set up in2014 by UK government and Capita, to manage and provide training in best practice (like ITIL), in methodologies formerly managed by APMG, and originally from the UK Office of Government Commerce (OGC).

I echo with the answer of Mohammed Thohamy Hussein..