Previous discussion:
(Some links may have expired.)
I read that as meaning only the 講演 – speeches and lectures – need to be paid for on an hourly basis in order to qualify. (How many novelists are paid by the hour?) The fact that the Enforcement Rules of the ITA sever the last part of the list from the rest of it supports this interpretation.
所得稅法施行細則 / Enforcement Rules of the Income Tax Act
Possibly.
Most likely.
Possibly.
That would be…
律師事務所或翻譯社，聘請個人撰寫、翻譯專利或其他文件以供執行業務或營業之需，所支付之報酬非屬稿費，應屬一般勞務報酬，按薪資所得課徵所得稅。（財政部68/08/11台財稅第35590號函）
For a law firm or translation agency hiring an individual to write or translate patents or other documents for the needs of business or professional practice, the remuneration paid is not in the category of gaofei and should be categorized as ordinary provision-of-labor remuneration, income tax being payable according to [the relevant provisions for] salary income.
Note the wording: 聘請 (hire), similar to 聘僱 (which implies hiring for employment) but apparently lacking an official definition. Also note that it says nothing about publication, implying that these documents would generally not be published.
This is the one I was thinking of in the other thread:
二、公私機關、團體、事業及各級學校，聘請學者、專家專題演講所給之鐘點費，屬所得稅法第4條第23款規定之講演鐘點費，可免納所得稅，但如與稿費、版稅、樂譜、作曲、編劇、漫畫等全年合計數，超過新臺幣180,000元以上部分，不在此限。三、公私機關、團體、事業及各級學校，開課或舉辦各項訓練班、講習會，及其他類似性質之活動，聘請授課人員講授課程，所發給之鐘點費，屬同法第14條第1項第3類所稱薪資所得。該授課人員並不以具備教授（包括副教授、講師、助教等）或教員身分者為限。（財政部74/04/23台財稅第14917號函）
For a public or private organization, group or enterprise or a school at any level, which holds classes or conducts training courses, seminars, or other activities of a similar nature, and which hires teaching personnel to teach the courses, the hourly fees thus paid are in the category of what the [Income Tax] Act Art. 14 Par. 1 Category 3 calls salary income. Such teaching personnel are not limited to the status of professor (including associate professor, lecturer, assistant professor etc.) or teacher [or instructor].
Again, it says these people are 聘請 by the educational institutions, and it goes further this time, characterizing them as 人員, which tends to be synonymous with employee or worker.
個人因翻譯書籍文件而取得之翻譯費，及因修改、增刪、調整文稿之文字計給之酬費，如改稿費、審查費、審訂費等，除屬基於僱用關係取得者屬薪資所得外，為稿費性質，可適用所得稅法第4條第23款規定，定額免納所得稅。（財政部86/02/26台財稅第861880788號函）
For an individual’s translation fees obtained due to translation of books/documents, as well as per-word fees for revising, adding/deleting, or adjusting the text of a draft, such as revision fees, review fees, examination fees etc., other than income obtained based on an employment relationship and thus categorized as salary income, it is of the nature of gaofei and can be subjected to the income tax exemption of the provisions of Income Tax Act Art. 4 Subpar. 23, for a certain amount.
This time it’s very clear: if the writing or editing is performed as part of an employment contract, it doesn’t count as gaofei for income tax purposes.
These three MOF letters are from 1979, 1985, and 1997 respectively, which suggests a gradual movement towards aligning the concept of 薪資所得 (salary income) with the concepts of 僱傭契約 (employment contracts) and 勞動契約 (labor contracts), though still leaving some wiggle room for other types of 勞務契約 (contracts for the provision of labor, including independent contracting) to be treated as producing salary income in some cases. Ergo, if the tax office thinks a business entity is paying you as if you were an employee (even a part-time one), even if the labor department doesn’t think so, the tax office can still deem the relevant income salary income, though I think in most cases if you’re truly not an employee the tax office will agree that the relevant income is not salary income. 
If you have a publication contract (出版契約) as in Civil Code Art. 515, I think you should be safe.
As always, if in doubt ask a lawyer. 