Yes, anyone can create a publisher account with AllTrack, regardless of whether you are an individual music creator, an individual that acts as a music publisher for other music creators or a professional 3rd party publishing company. There is no requirement to have a legal entity or company to become a music publisher, and creating a music publisher with AllTrack does not create a legal entity or a company for you. Creating a publisher with AllTrack simply opens a new publisher account for you that is able to receive the publisher's share of performance royalties.
For a music creator, creating a publisher account is sometimes referred to as "setting up your publishing". With AllTrack, if you are an independent creator, there is no requirement for you to setup a publisher to receive 100% of your combined writer and publisher shares of performance royalties. However, there are many benefits to setting up an AllTrack publisher account which you can read about here.
You can create a free AllTrack music publisher account here.