In the past I think most designers worked for yarn companies and patterns were mainly a way of selling yarn. In Norway, most yarn shops wouldn't sell patterns unless you bought the yarn to go with it. If you bought a pattern booklet you had to buy the yarn for at least one pattern from the booklet. I assume things were similar here in the UK. These rules probably did encourage copying of patterns.Most, I guess, were employed by yarn companies. So if you shared a pattern with a friend the designer still got paid.
These days, most designers, myself included, make a living from designing and selling our patterns. Few yarn companies employ fulltime designers and use freelancers instead.
Since the internet happened and particularly since Ravelry started many designers choose to self-publish. Its an easy way to get started as a new designer. Rather than waiting for a yarn company or magazine to commission you to design for them, you can design something, write up the pattern and sell it on Ravelry or other sites. Ravelry also has a huge number of free patterns.
For some self publishing designers it may be a part-time job but for others it makes a big contribution to supporting their families and for many designers it's their only income. In the UK, most patterns are around £3 each. When you think about the cost of yarn £3 isn't that much to pay for a pattern but still there is this sense of 'I shouldn't have to pay for a pattern' in certain circles. But for each pattern shared between knitters, the designer loses out. If designers can't make a living from pattern sales then they can't afford to continue to do that job.
I'm not going to give legal advice as I'm not a lawyer. So what I'm going to say below is my interpretation of what's ethically acceptable.
When you purchase a pattern it's for your use only. It's not okay to save the pdf on your computer and print it out or e-mail it to your friends or to your whole knitting group. The same goes for print patterns but PDFs are easier to share.
If you buy a book or a print pattern and lend that copy to a friend then that's ok, if you make a copy or give it to a friend and you keep the original, then that's not okay. If there is only one copy then only one person can knit from it at a time. Of course you can copy a pattern for your own use, like having a copy you can scribble on etc. ETA: just to clarify, I mean copy a pattern you already own so that you can keep original safe and makes notes on the copy or have a spare copy if you lose original etc.
I recently overheard a conversation at my local knitting group. One lady was admiring another lady's shawl. It turned out several of our members were knitting the same shawl. One knitter offered to email the pattern to a couple of people, so I asked if it was a free pattern and was told no, it was for sale on Ravelry. I thought for a moment and then made a comment about how sharing patterns was depriving the designer of income!
Now I must admit, I felt extremely uncomfortable. I wasn't sure if this offer to share the pattern was done because they thought it was okay and there was nothing wrong with it or if it was done in the full knowledge of the fact that sharing the pattern was wrong.
One of our members shared a story relating to the decline in machine knitting in the UK. She said that machine knitters would copy patterns and share them among their knitting groups and as a result machine knitting designers weren't making a living and had to find other ways of earning a living. As a result of this, finding modern machine knitting patterns in this country is extremely hard. And that the same would happen to hand-knitting unless knitters were willing to support designers and pay for patterns.
It costs a lot of money to publish a pattern. I spend hours writing the pattern, I pay a sample knitter to knit a sample for me, I pay my daughters to model for me, I probably should pay a photographer but can't afford to. I pay a tech editor to edit the pattern and check for accuracy. I have a desk top publising software programme and charting software programme I use. This all adds up and my only way of recouping all that money spent is to sell the pattern and hopefully make enough money on it to pay myself!
So, if you enjoy knitting designs by independent designers, pay for it. Don't offer to email it to your knitting friends but encourage them to buy their own copy. That way designers will make money and can continue to design fabulous patterns. Help us educate knitters to appreciate and be willing to pay for the work that goes into knitting.